In a large packet switching system having hundreds of thousands of terminals interconnected by a large number of switching networks with the switching networks themselves being interconnected by high speed digital transmission links, it is desirable to be able to accurately and efficiently monitor the traffic which is being carried by each digital transmission link. In prior art packet switching systems which are made up of general purpose computers interconnected by transmission links, traffic load monitoring is performed by the same computer that is doing packet switching. Because of the real time constraints placed on the computer having to perform both the packet switching and load monitoring functions, it is not feasible to implement accurate algorithms for measuring the load; instead, only algorithms which approximated the load on a particular transmission link are utilized. Such algorithms count the number of packets transmitted within a fixed period of time, rather than the actual time required to transmit packets over the transmission link, and compare this number with some predetermined value of load. Since the length of each packet varies, these algorithms do not give an accurate measurement of load.
Accurate traffic load monitoring is desirable in packet switching systems because among other reasons there exists more than one potential route between any two points within the system. Thus, if the load is accurately known, it is possible to balance the load throughout the system. Also, in a system utilizing high speed digital transmission facilities as the interconnecting links, it is desirable that the measurement of traffic load be done in such a way that this measurement does not delay the transmission of the packets.